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<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>arr.map()</title>
</head>

<body>

</body>
<script>
    function pow(x) {
        return x * x;
    }
    var nums = [1,2,3];
    nums = nums.map(pow);
    console.log(nums);
</script>

</html>